When running casing or liner into a predrilled bore hole, it is desirable that the bore hole will have been drilled with intended cylindricity, to its designed diameter, and without marked deviations, such as doglegs, along its path. Unfortunately, due to transitions between formations, irregularities such as stringers within a formation, the use of out-of-tolerance drill bits, damage to drill bits after running into the bore hole, bottom hole assembly (BHA) configurations employed by the driller, and various other factors, the ideal bore hole is rarely achieved.
Therefore, it is desirable to provide the casing or liner being run into the existing bore hole with a cutting structure at the leading end thereof to enable enlargement, as necessary, of portions of the bore hole so that the casing or liner may be run into the bore hole to the full extent intended. Various approaches have been attempted in the past to provide a casing or liner string with a reaming capability, with inconsistent results.